Method of modifying a fluoropolymer and articles thereby

ABSTRACT

A fluoropolymer is modified by contacting it with a modifying composition preparable from components comprising a phase transfer catalyst and at least one of a sulfide or disulfide salt, and heating the modifying composition. The modified fluoropolymer is useful in the preparation of composite articles.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.10/681,909, filed Oct. 9, 2003 now Pat. No. 6,986,947, the disclosure ofwhich is herein incorporated by reference.

BACKGROUND

Fluoropolymers are generally renowned for their chemical and physicalinertness. Indeed, their excellent barrier properties and hydrophobiccharacter are extensively exploited for applications such as moistureand noxious gas barriers, anti-corrosion and non-stick coatings.Examples of commonly used fluoropolymers includepolytetrafluoroethylene, polyvinylidene difluoride, and copolymers ofvinylidene difluoride with tetrafluoroethylene and hexafluoropropylene.

Multi-layer constructions containing fluoropolymers enjoy wideindustrial application. Such constructions find utility, for example, infuel line hoses and related containers and hoses or gaskets in thechemical processing field. Adhesion between the layers of amulti-layered article may need to meet various performance standardsdepending on the use of the finished article. However, in bondingapplications between a fluoropolymer film and a non-fluorinated polymerfilm, the non-adhesive qualities of fluoropolymers can make it difficultto obtain a strong laminated bond.

Various approaches have been used to modify the surface of fluoropolymersubstrates, including harsh chemical treatments such as alkali metalreduction (e.g., using alkali metal in liquid ammonia orsodium-naphthalene in glyme), and in the case of polyvinylidenedifluoride, using concentrated alkali metal hydroxide solutions in thepresence of a phase transfer catalyst. Other approaches includeradiation treatments such as laser induced surface modification, andphotoreduction of fluoropolymer substrates.

Each of the above processes has drawbacks. For example, alkali metalreduction requires maintenance of moisture-free conditions, theconcentrated (8 N) alkali metal hydroxide process is relatively slow,and radiation induced processes require a radiation source that may becostly (e.g., a laser), and/or may not be well-suited to opaquesubstrates (e.g., photochemical reduction in the presence of electrondonors).

It would be desirable to have new methods for chemically modifyingfluoropolymers. It would also be useful to have new methods forchemically modifying surfaces of fluoropolymer substrates so that theycan be bonded to non-fluorinated polymeric substrates, particularly ifsuch methods are easily and quickly carried out and result in stronglaminated bonds.

SUMMARY

In one aspect, the present invention provides a method of modifying afluoropolymer comprising:

contacting the fluoropolymer with a modifying composition preparablefrom components comprising a phase transfer catalyst, at least one of asulfide or polysulfide salt or anionic conjugate acid thereof, and aliquid vehicle; and

heating the modifying composition at a temperature of at least about 40degrees Celsius while in contact with the fluoropolymer, wherein thefluoropolymer has a backbone comprising subunits having the structure—CH₂CFX—, wherein X represents H, Cl, or F.

In another aspect, the present invention provides method of preparing acomposite article comprising:

providing a first substrate having a surface comprising fluoropolymer;

contacting the surface of the first substrate with a modifyingcomposition preparable from components comprising a phase transfercatalyst, at least one of a sulfide or polysulfide salt or anionicconjugate acid thereof, and a liquid vehicle, wherein the fluoropolymerhas a backbone comprising subunits having the structure —CH₂CFX—,wherein X represents H, Cl, or F; and

bonding the first substrate to a second substrate to provide a compositearticle, wherein the method is carried out in the substantial absence ofactinic radiation.

In some embodiments, the fluoropolymer backbone further comprisesmonomeric units having at least one of the formulas —CF₂CF₂—, —CH₂CH₂—,—CF₂CF(CF₃)—, or —CH₂CH(CH₃)—.

In yet another aspect, a first substrate has a surface that comprisesmodified fluoropolymer according to the present invention. In someembodiments, the surface of the first substrate may be bonded to asecond substrate to form a composite article.

These and other aspects of the invention will be apparent from thedetailed description below. In no event, however, should the abovesummaries be construed as limitations on the claimed subject matter,which subject matter is defined solely by the attached claims, as may beamended during prosecution.

As used in this application:

“fluoropolymer” means a polymer having fluorine atoms on its backboneand a fluorine content of at least 20 percent by weight;

“monomer” means a compound that can undergo polymerization therebycontributing constitutional units to the essential structure of apolymer;

“monomeric unit” means the largest constitutional unit contributed by asingle monomer molecule to the structure of a polymer;

“polymer” means a chemical compound comprising at least five monomericunits, which monomeric units may be the same or different;

“polymer backbone” means the longest chain of connected monomeric unitsin a polymer;

“soluble” means dissolvable in a chosen liquid vehicle at concentrationsexceeding about 0.001 mole per liter at 25° C.; and

“subunit” means a divalent group that is contained within a polymerbackbone.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a cross-sectional side view of an exemplary compositearticle according to the present invention.

DETAILED DESCRIPTION

Useful fluoropolymers have a backbone comprising one or more subunitshaving the structure —CH₂CFX—, wherein X represents H, Cl, or F. Thesubunits may, or may not, correspond to monomeric units.

Useful fluoropolymers include, for example, polyvinyl fluoride,polyvinylidene difluoride, and copolymers of vinyl fluoride,chlorotrifluoroethylene, and/or vinylidene difluoride (i.e., VDF) withone or more ethylenically unsaturated monomers such as alkenes (e.g.,ethylene, propylene, butylene, and 1-octene), chloroalkenes (e.g., vinylchloride and tetrachloroethylene), chlorofluoroalkenes (e.g.,chlorotrifluoroethylene, 3-chloropentafluoropropene,dichlorodifluoroethylene, and 1,1-dichlorofluoroethylene), fluoroalkenes(e.g., trifluoroethylene, tetrafluoroethylene (i.e., TFE),1-hydropentafluoropropene, 2-hydropentafluoropropene,hexafluoropropylene (i.e. HFP), and vinyl fluoride), perfluoroalkoxyvinyl ethers (e.g., CF₃OCF₂CF₂CF₂OCF═CF₂); perfluoroalkyl vinyl ethers(e.g., CF₃OCF═CF₂ and CF₃CF₂CF₂OCF═CF₂), perfluoro-1,3 -dioxoles such asthose described in U.S. Pat. No. 4,558,142 (Squire), fluorinateddiolefins (e.g., perfluorodiallyl ether or perfluoro-1,3-butadiene), andcombinations thereof.

Commercially available vinyl fluoride fluoropolymers include, forexample, those marketed under the trade designation “TEDLAR” by E.I. duPont de Nemours & Company, Wilmington, Del.

Commercially available vinylidene difluoride-containing fluoropolymersinclude, for example, those fluoropolymers having the trade designation“THV” (e.g., “THV 200”, “THV 400”, “THVG”, “THV 610”, or “THV 800”) asmarketed by Dyneon, St. Paul, Minn.; “KYNAR” (e.g., “KYNAR 740”) asmarketed by Atofina, Philadelphia, Pa.; “HYLAR” (e.g., “HYLAR 700”) asmarketed by Ausimont USA, Morristown, N.J.; and “FLUOREL” (e.g.,“FLUOREL FC-2178”) as marketed by Dyneon.

The fluoropolymer may be melt-processable, for example, as in the caseof polyvinylidene difluoride; copolymers of tetrafluoroethylene,hexafluoropropylene, and vinylidene difluoride (e.g., those marketed byDyneon LLC under the trade designation “THV”); copolymers oftetrafluoroethylene and hexafluoropropylene; and other melt-processablefluoroplastics; or the fluoropolymer may not be melt-processable, forexample, as in the case of polytetrafluoroethylene, copolymers of TFEand low levels of fluorinated vinyl ethers), and cured fluoroelastomers.

One useful fluoropolymer includes monomeric units derived from at leastTFE and VDF in which the amount of VDF is at least 0.1, 3, or 10 percentby weight, but less than 15 or 20 percent by weight, with the remainderbeing TFE derived monomeric units.

Useful fluoropolymers include those copolymers having HFP and VDFmonomeric units, for example, those copolymers in which the amount ofVDF monomeric units is at least 0.1, 3, or 10 percent by weight, butless than 15 or 20 percent by weight, with the remainder of the polymerweight being HFP monomeric units.

Useful fluoropolymers also include copolymers of HFP, TFE, and VDF(i.e., THV). These polymers may have, for example, VDF monomeric unitsin a range of from at least about 2, 10, or 20 percent by weight up to30, 40, or even 50 percent by weight, and HFP monomeric units in a rangeof from at least about 5, 10, or 15 percent by weight up to about 20,25, or even 30 percent by weight, with the remainder of the weight ofthe polymer being TFE monomeric units. Examples of commerciallyavailable THV polymers include those marketed by Dyneon, LLC under thetrade designations “DYNEON THV 2030G FLUOROTHERMOPLASTIC”, “DYNEON THV220 FLUOROTHERMOPLASTIC”, “DYNEON THV 340C FLUOROTHERMOPLASTIC”, “DYNEONTHV 415 FLUOROTHERMOPLASTIC”, “DYNEON THV 500A FLUOROTHERMOPLASTIC”,“DYNEON THV 610G FLUOROTHERMOPLASTIC”, or “DYNEON THV 810GFLUOROTHERMOPLASTIC”.

Useful fluoropolymers also include copolymers of ethylene, TFE, and HFP.These polymers may have, for example, ethylene monomeric units in arange of from at least about 2, 10, or 20 percent by weight up to 30,40, or even 50 percent by weight, and HFP monomeric units in a range offrom at least about 5, 10, or 15 percent by weight up to about 20, 25,or even 30 percent by weight, with the remainder of the weight of thepolymer being TFE monomeric units. Such polymers are marketed, forexample, under the trade designation “DYNEON FLUOROTHERMOPLASTIC HTE”(e.g., “DYNEON FLUOROTHERMOPLASTIC HTE X 1510” or “DYNEONFLUOROTHERMOPLASTIC HTE X 1705”) by Dyneon LLC.

Useful fluoropolymers also include copolymers of tetrafluoroethylene andpropylene (TFE/P). These copolymers may have, for example, TFE monomericunits in a range of from at least about 20, 30 or 40 percent by weightup to about 50, 65, or even 80 percent by weight, with the remainder ofthe weight of the polymer being propylene monomeric units. Such polymersare commercially available, for example, under the trade designations“AFLAS” (e.g., “AFLAS TFE ELASTOMER FA 100H”, “AFLAS TFE ELASTOMER FA150C”, “AFLAS TFE ELASTOMER FA 150L”, or “AFLAS TFE ELASTOMER FA 150P”)as marketed by Dyneon, LLC, or “VITON” (e.g., “VITON VTR-7480” or “VITONVTR-7512”) as marketed by E.I. du Pont de Nemours & Company, Wilmington,Del.

Useful fluoropolymers also include copolymers of ethylene and TFE (i.e.,“ETFE”). These copolymers may have, for example, TFE monomeric units ina range of from at least about 20, 30 or 40 percent by weight up toabout 50, 65, or even 80 percent by weight, with the remainder of theweight of the polymer being propylene monomeric units. Such polymers maybe obtained commercially, for example, as marketed under the tradedesignations “DYNEON FLUOROTHERMOPLASTIC ET 6210J”, “DYNEONFLUOROTHERMOPLASTIC ET 6235”, or “DYNEON FLUOROTHERMOPLASTIC ET 6240J”by Dyneon LLC.

VDF-containing fluoropolymers can be prepared using emulsionpolymerization techniques as described, for example, in U.S. Pat. No.4,338,237 (Sulzbach et al.) or U.S. Pat. No. 5,285,002 (Grootaert), thedisclosures of which are incorporated herein by reference.

The fluoropolymer may have any form. For example, the fluoropolymer maycomprise a solution or dispersion, or it may have a solid form such as,for example, a block, film (e.g., including sheets, webs, and tapes), ora molded article. In the case of solid forms, methods according to thepresent invention are useful for modifying one or more surfaces of thesolid form (e.g., one or more major surfaces of a film), while in thecase of emulsions or solutions, methods of the present invention areuseful for modifying the bulk polymer.

The fluoropolymer is modified by contacting it with a modifyingcomposition that comprises and/or is preparable from a phase transfercatalyst, at least one of a sulfide or polysulfide salt or an anionicconjugate acid thereof, and heating the contacted combination at atemperature at or above ambient temperature (e.g., 23° C.). Typically,heating at a temperature of at least 40° C. results in useful rates ofmodification, with even more rapid rates resulting at highertemperatures such as, for example, at least 60° C. or even at least 80°C. The duration of heating may be for as little as at least 1, 15, 30 or60 seconds up to and including 120 or even 300 seconds, although longerand shorter durations may also be useful depending on specificconditions and the degree of modification sought. He ating may beprovided by ambient conditions or conventional means such as, forexample, ovens (e.g., convection or forced air), radiant heaters, hotplates, microwave heaters, heated vessels, heated rollers, andcombinations thereof.

Advantageously, methods according to the present invention do notrequire light in order to be effective, which makes them useful inapplications where it is difficult to use light (e.g., closed metalreaction vessels) or where exposure to light is undesirable (e.g., lightdegradable materials). Thus, methods according to the present inventionmay be carried out in the substantial absence of actinic radiation(i.e., in the absence of actinic radiation other than that adventitiousactinic radiation caused by ambient lighting conditions such as, forexample, sunlight, candles, lamps, lanterns, and/or incandescent orfluorescent room lighting). As used herein “actinic radiation” meanslight having a wavelength of from at least 200 nanometers up to andincluding 400 nanometers.

Useful phase transfer catalysts include, for example, organosulfoniumsalts (e.g., triarylsulfonium salts such as triphenylsulfonium chloride,trichlorophenylsufonium bromide, tritolylsulfonium chloride, anddiphenyl-(4-thiophenyl)phenylsulfonium hexafluorophosphate;trialkylsulfonium salts such as tributylsulfonium chloride,ethyldibutylsulfonium bromide; mixed alkylarylsulfonium salts such asmethyldiphenylsulfonium p-toluenesulfonate, ethyloctylphenylsulfoniumchloride, butyldiphenylsulfonium hexafluorophosphate; and combinationsand substituted derivatives of the foregoing); organoarsonium salts(e.g., tetraarylarsonium salts such as tetraphenylarsonium chloride andtetratolylarsonium bromide; tetraalkylarsonium salts such astetramethylarsonium iodide, octyltrimethylarsonium bromide, andtetraethylarsonium chloride; mixed alkylarylarsonium salts such asbutyltriphenylarsonium iodide; and combinations and substitutedderivatives of the foregoing); organoantimonium salts (e.g.,tetraarylantimonium salts such as tetraphenylantimonium chloride andtritolylantimonium chloride; tetraalkylantimonium salts such astetramethylantimonium iodide, octyltrimethylantimonium bromide, andtetraethylantimonium chloride; mixed alkylarylantimonium salts such asbutyldiphenylantimonium iodide; and combinations and substitutedderivatives of the foregoing); organoiodonium salts (e.g.,dirayliodonium salts such as diphenyliodonium chloride, diphenyliodoniumhexafluoroantimonate, and ditolyliodonium chloride); organophosphoniumsalts (e.g., quaternary phosphonium salts such as tetraalkylphosphoniumsalts, aralkyltriarylphosphonium salts, and aryltrialkylphosphoniumsalts); organoammonium salts (e.g., quaternary ammonium salts such astetraalkylammonium salts, aralkyltriarylammonium salts, andaryltrialkylammonium salts); crown ethers; and combinations of thereof.

Further details concerning phase transfer catalysts may be found in, forexample, U.S. Pat. No. 4,233,421 (Worm), U.S. Pat. No. 4,912,171(Grootaert et al.), U.S. Pat. No. 5,086,123 (Guenthner et al.) and U.S.Pat. No. 5,262,490 (Kolb et al.).

Phosphonium and ammonium salt phase transfer catalysts are typicallyrelatively inexpensive and easily obtained, and therefore are typicallywell-suited for use in practice of the present invention. Usefultetraalkylphosphonium or tetraalkylammonium salts may have as few as 4carbon atoms, up to at least 16, 20, 24 carbon atoms or even more.

Quaternary ammonium salts and quaternary phosphonium salts may have anysuitable anionic counterion that permits at least partial solubility ofthe salt in the liquid vehicle. Examples of suitable counterions includehalides (e.g., fluoride, chloride, bromide, iodide), nitrate, bisulfate,sulfate, carbonate, bicarbonate, phosphate, alkylphosphonate, mesylate,tosylate, and combinations thereof.

Examples of useful commercially available quaternary ammonium saltsinclude methyltributylammonium chloride, methyltricaprylylammoniumchloride, tetrabutylammonium bromide, tetrabutylammonium hydrogensulfate, tetraethylammonium bromide, tetraethylammonium hydroxide,tetramethylammonium chloride, tetramethylammonium iodide,tributylethylammonium bromide, tributylmethylammonium chloride,triethylbutylammonium bromide, benzyltributylammonium chloride,benzyltriethylammonium chloride, benzyltrimethylammonium chloride,phenyltrimethylammonium chloride, tetraoctylammonium chloride,triphenylbenzylammonium bromide, triphenylbenzylammonium acetate,triphenylbenzylammonium benzoate, triphenylisobutylammonium bromide,trioctyl-n-butylammonium chloride, trioctylbenzylammonium chloride,trioctylbenzylammonium acetate, triphenyl-2,4-dichlorobenzylammoniumchloride, trioctylmethoxyethoxyethylammonium chloride,triphenylethoxycarbonylmethylammonium chloride, triphenylallylammoniumchloride, and 1-butylpyridinium chloride.

Examples of useful commercially available quaternary ammonium saltsinclude benzyltriphenylphosphonium chloride, butyltriphenylphosphoniumbromide, ethyltriphenylphosphonium bromide, ethyltriphenylphosphoniumchloride, ethyltriphenylphosphonium iodide, methyltriphenylphosphoniumbromide, methyltriphenylphosphonium chloride, methyltriphenylphosphoniumiodide, tetrabutylphosphonium bromide, tetraphenylphosphonium bromide,tetraoctylphosphonium chloride, triphenylbenzylphosphonium bromide,triphenylbenzylphosphonium acetate, triphenylbenzylphosphonium benzoate,triphenylisobutylphosphonium bromide, trioctyl-n-butylphosphoniumchloride, trioctylbenzylphosphonium chloride, trioctylbenzylphosphoniumacetate, triphenyl-2,4-dichlorobenzylphosphonium chloride,trioctylmethoxyethoxyethylphosphonium chloride,triphenylethoxycarbonylmethylphosphonium chloride, andtriphenylallylphosphonium chloride.

Useful crown ethers include macrocyclic polyethers comprising ethyleneoxide units which can coordinate to a centrally located metal atom viathe oxygen atoms of the ethers such as, for example, 18-crown-6 ether,15-crown-5 ether, dicyclohexyl-18-crown-6 ether, and dibenzo-18-crown-6ether, 12-crown-4 ether, 21-crown-7 ether, benzo-15-crown-5 ether, whichmay be readily obtained from commercial sources.

Typical concentrations of phase transfer catalysts in the modifyingcomposition are in a range of from at least 0.001 up to 0.1 mole perliter, although other amounts may also be used.

Useful sulfide and polysulfide salts include those salts that have atleast partial solubility in at least one liquid vehicle, and include,for example, salts comprising at least one sulfide or polysulfide (e.g.,disulfide, trisulfide, or tetrasulfide) anion, or an anionic conjugateacid of sulfide or polysulfide (e.g., bisulfide), or a combinationthereof, in combination with at least one cationic counterion. Usefulcationic counterions include, for example, alkali metal ions (e.g., Na⁺,K⁺, Li⁺, Cs⁺), alkaline earth ions (e.g., Mg²⁺, Ca²⁺), NH4+, quaternaryammonium (e.g., tetraalkylammonium, aryltrialkylammonium,aralkyltrialkylammonium, tetraaryl ammonium) ions, and quaternaryphosphonium (e.g., tetraalkylphosphonium, aryltrialkylphosphonium,aralkyltrialkylphosphonium, tetraarylphosphonium) ions, and combinationsthereof. Typical concentrations of sulfide or polysulfide salt in themodifying composition are in a range of from at least 0.001 up to 0.1mole per liter, although other amounts may also be used.

Sulfide ions may be provided by various precursors that form sulfide inthe presence of water (e.g., in the presence of a base catalyst).Examples of such precursors include thioacids, thioureas, andthioketones.

In one useful embodiment, a sulfide or polysulfide anion, or anionicconjugate acid thereof may be paired with a cation of at least one ofthe phase transfer catalyst described above to form a salt. Such saltsmay simultaneously serve as a sulfide or polysulfide salts (or ananionic conjugate acid thereof) and a phase transfer catalyst.

Typically, the liquid vehicle should be chosen such that it does notdissolve or significantly swell the polymeric substrate, but is at leastpartially effective to dissolve the phase transfer catalyst and sulfidesalt, polysulfide salt, or anionic conjugate acid thereof. The liquidvehicle may comprise water, organic solvent (e.g., alcohols such asmethanol, ethanol, isopropanol; ketones and ketoalcohols such asacetone, methyl ethyl ketone, diacetone alcohol; esters such as ethylacetate and ethyl lactate; polyhydric alcohols such as ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol, butyleneglycol, 1,4-butanediol, 1,2,4-butanetriol, 1,5-pentanediol,1,2,6-hexanetriol, hexylene glycol, glycerol, glycerol ethoxylate, andtrimethylopropane ethoxylate; lower alkyl ethers, such as ethyleneglycol monomethyl or monoethyl ether, diethylene glycol methyl or ethylether, and triethylene glycol monomethyl and monoethyl ether; andcombinations thereof), or a combination thereof.

The modifying composition may include optional additives such as, forexample, thixotropes, thickeners, gelation agents, latex particles,fibers, inorganic particles, an emulsifiable phase, woven or nonwovenmaterials, and/or nucleophiles (i.e., species that have a preferentialattraction to regions of low electron density) that may become graftedto the fluoropolymer. Exemplary nucleophiles include water, hydroxide,alcohols, alkoxides, cyanide, cyanate, halide (e.g., chloride, bromide,iodide).

Typically, the modifying composition may be prepared by combining (e.g.,with mixing) the phase transfer catalyst, sulfide or polysulfide salt oran anionic conjugate acid thereof, liquid vehicle, and optionaladditives. In some cases, heating may be useful to facilitate dissolvingone or more of the components in the liquid vehicle.

Varying degrees of surface modification may be obtained, for example, byvarying the length of time that the modifying composition and thefluoropolymer are in contact and/or by varying the temperature of theprocess. The degree of surface modification may be determined by variouswell known surface analysis techniques including, but not limited to,Attenuated Total internal Reflectance Infrared Spectroscopy (ATR IR) andElectron Scattering for Chemical Analysis (ESCA), as well as contactangle measurements.

Once the fluoropolymer is modified, whether in the bulk phase, or at asurface of a solid fluoropolymer substrate (e.g., a film or block), itmay be bonded to a second substrate. Such bonding may be accomplished,for example, using glue or adhesive (e.g., pressure-sensitive,thermosetting, hot melt) and/or by laminating under pressure and/or withheating using conventional methods, and resulting in a composite articleas shown in the drawing, wherein composite article 100 comprises afluoropolymer substrate 120 having a modified surface 160, whichcontacts optional adhesive layer 150 and surface 140 of second substrate130.

Suitable heat sources for bonding include, for example, ovens, heatedrollers, heated presses, infrared radiation sources, flame, and thelike. Suitable pressure for bonding may be provided by, for example,presses, nip rollers, and the like. The necessary amounts of heat andpressure will depend on the specific materials to be bonded, and istypically easily determined by empirical methods.

The second substrate may comprise, for example, a polymer (e.g., as afilm or block), metal, glass, or other material. If the second substrateis a polymer film such as a fluoropolymer or a non-fluorinated polymer,it may be the same as, or different from, the fluoropolymer substrate.The second substrate may have polar groups on its surface that aid informing a strong adhesive bond. Polar groups may be introduced by knowntechniques including, for example, corona treatment.

Exemplary polymer films that may be used as a second substrate includefilms comprising thermoplastic polymers such as polyamides(e.g.,nylon-6, nylon-6,6, nylon-11, and nylon-12), polyolefins (e.g.,polyethylene, polypropylene), copolymers of olefins with ethylenicallyunsaturated monomers (e.g., ethylene vinyl acetate, anhydride modifiedpolyethylene polymers, anhydride modified polypropylene polymers),polyethers, polyurethanes, polyesters, polyimides, polystyrene,polycarbonates, polyketones, polyureas, acrylics, and combinationsthereof; elastomers such as acrylonitrile butadiene rubber, butadienerubber, chlorinated or chlorosulfonated polyethylene, chloroprene,ethylene-propylene monomer rubber, ethylene-propylene-diene monomerrubber, epichlorohydrin rubber, polyisobutylene, polyisoprene,polyurethane, silicone rubber, styrene-butadiene rubber,ethylene-acrylate copolymer rubber, ethylene-vinyl acetate rubber, andcombinations thereof; and combinations thereof.

The polymer film may comprise one or more additives such as, forexample, fillers, plasticizers, antioxidants, or light stabilizers.

Objects and advantages of this invention are further illustrated by thefollowing non-limiting examples, but the particular materials andamounts thereof recited in these examples, as well as other conditionsand details, should not be construed to unduly limit this invention.

EXAMPLES

Unless otherwise noted, all reagents used in the examples were obtained,or are available, from general chemical suppliers such as Sigma-AldrichCorporation, Saint Louis, Mo. or may be synthesized by conventionalmethods.

The following examples and tests were carried out under ambientconditions (21–25° C.) unless otherwise specified.

In the Examples:

“Me” means methyl; “Bu” means n-butyl; “Pentyl” means n-pentyl; “Hexyl”means n-hexyl; and “Octyl” means n-octyl;

“g” means grams, and “mL” means milliliters;

“NM” in the tables means “not measured”;

“NA” in the Tables means “not applicable”;

“FP1” refers to a 16–20 mils (0.41–0.51 mm) thick extruded film of acopolymer of 60.0 percent by weight of TFE, 18.0 percent by weight HFP,and 22.0 percent by weight of VDF, T_(m)=165° C.; prepared generallyaccording to the procedure of U.S. Pat. No. 6,242,548 (Duchesne et al.).

“FP2” refers to a 16–20 mils (0.41–0.51 mm) thick extruded film of acopolymer of 73.0 percent by weight TFE, 11.5 percent by weight HFP,11.5 percent by weight VDF, and 4.0 percent by weight of perfluoropropylvinyl ether, T_(m)=222° C., MFI=4.8; prepared generally according to theprocedure of U.S. Pat. No. 6,242,548 (Duchesne et al.);

“FP3” refers to a 16–20 mils (0.41–0.51 mm) thick film of polyvinylidenedifluoride obtained by hot pressing PVDF resin obtained under the tradedesignation “SOLEF 1010” from Solvay, S. A., Brussels, Belgium under thetrade designation “KYNAR 761”;

“FP4” refers to a 16–20 mils (0.41–0.51 mm) thick extruded film of acopolymer of ethylene, TFE, and HFP obtained under the trade designation“DYNEON FLUOROTHERMOPLASTIC HTE” from Dyneon, LLC;

“FP5” refers to a 3 mils (0.08 mm) thick extruded film of polyvinylfluoride obtained under the trade designation “TEDLAR” from E.I. du Pontde Nemours & Company;

“P1” refers to a 16–20 mils (0.41–0.51 mm) thick hot pressed film ofnylon-12 having a Vicat softening point of 140° C. obtained under thetrade designation “VESTAMID L2140”, commercially available from Creanova(Somerset, N.J.);

“P2” refers to a 16–20 mils (0.41–0.51 mm) thick hot pressed film of anacid modified ethylene-vinyl acetate copolymer having the tradedesignation “BYNEL 3101” obtained from E.I. du Pont de Nemours and Co.;

“ADH1” refers to a bisphenol A epoxy resin obtained under the tradedesignation “EPON 828” from Resolution Performance Products, Houston,Tex.;

“ADH2” refers to a cycloaliphatic epoxy resin obtained under the tradedesignation “ERL 4221” from Dow Chemical Company, Midland, Mich.;

“ADH3” refers to a novolac epoxy resin obtained under the tradedesignation “DEN 431” from Dow Chemical Company;

“ADH4” refers to an ethylene acrylic acid resin obtained under the tradedesignation “THERMO-BOND FILM 406” from 3M Company;

“ADH5” refers to an ethylene acrylic acid resin obtained under the tradedesignation “THERMO-BOND FILM 557” from 3M Company;

“ADH6” refers to a polyester resin obtained under the trade designation“THERMO-BOND FILM 615” from 3M Company;

“ADH7” refers to a polyester resin obtained under the trade designation“THERMO-BOND FILM 668” from 3M Company;

“ADH8” refers to a polyolefin resin obtained under the trade designation“THERMO-BOND FILM 845” from 3M Company; and

“ADH9” refers to an acrylic pressure-sensitive adhesive obtained underthe trade designation “3M ADHESIVE TRANSFER TAPE 300” from 3M Company;

“PTC1” refers to methyltrialkyl(C₈-C₁₀)ammonium chloride obtained underthe trade designation “ADOGEN 464” from Sigma-Aldrich Corporation.

Preparation of Sodium Disulfide

Sodium disulfide used in the examples was prepared according to thefollowing procedure: Into a flask was placed sodium sulfide nonahydratecrystal (24.0 g, 0.1 mole) and sulfur (3.2 g, 0.1 mole), the mixture washeated by a steam bath until the sulfur was completely dissolved. Thereaction product was cooled to room temperature to give sodium disulfideas orange crystals.

ESCA Analysis

The instrument used in the analysis was a twin-analyzer ESCA apparatuswith an un-monochromatized Al source; photoemission was detected at ascattering angle of 45 degrees with respect to the surface normal,unless otherwise specified.

T-Peel Test

Peel strength between the layers was measured in generally in accordancewith D1876-01 (2001) “Standard Test Method for Peel Resistance ofAdhesives (T-Peel Test)”. Samples were cut into strips 25.4 mm wide byabout 2 to 2.5 inches (5 to 6.3 cm) long.

A Model 1125 tester (available from Instron Corporation, Canton, Mass.)at 100 mm/minute crosshead speed was used as the test device. As thelayers were separated, the average peel strength of the middle 80percent of the sample was measured. The values from the first 10 percentand the last 10 percent distance of the crosshead travel were omitted.When the samples broke within the material without separating the layersat the bonding interface, the peak value was used instead of the averagenumber. Reported peel strengths, calculated as the average load measuredduring each peel test and reported in Newtons/meter (N/m) of samplewidth, represent an average of at least two measurements obtained fromidentical samples.

REFERENCE EXAMPLE 1

Two glass thermometers (red alcohol, and mercury types), not transparentto 254 nanometer radiation, were placed for 10 minutes at a distance of2 inches (5 centimeters) under a flat bank of six G15T8 germicidal bulbs(an ultraviolet radiation source with maximum intensity at a wavelengthof 254 nanometers) spaced on 2 inch (5 cm) centers obtained from GeneralElectric Company, Schenectady, N.Y. The temperature rose from an initialtemperature of 23° C. and leveled off at a final temperature of 29° C.

COMPARATIVE EXAMPLE 1

Bu₄PBr (1.0 g) and 3.0 g potassium hydroxide (KOH) were added to 60 mlwater and stirred for 20 minutes at room temperature. A piece of FP1(2.0 inches by 1.0 inch (5.1 cm by 2.5 cm)) was submerged in thesolution for 5 minutes at 25° C. The treated fluoropolymer film was thenremoved, washed repeatedly in water (6×100 mL) by stirring the waterwith the film, washed twice with isopropanol and dried. The sample wasthen analyzed by ESCA to determine the chemical modifying composition ofthe treated surface. The results of the ESCA analysis are reported inTable 1.

COMPARATIVE EXAMPLE 2

The procedure of Comparative Example 1 was repeated, except that thetemperature of the treatment solution was held at 80° C. for 5 minuteswhile in contact with the fluoropolymer film. The treated surface of thefilm was analyzed by ESCA, and the results are reported in Table 1.

The treated fluoropolymer film was placed in a screw cap vial containing30 mL of 0.5 molar bromine in carbon tetrachloride and was held at 25°C. for 20 minutes. The film coupon was removed from the brominesolution, washed with carbon tetrachloride followed by dichloromethane,and dried. The treated surface of the film was analyzed by ESCA, and theresults are shown in Table 1.

EXAMPLE 1

Bu₄PBr (1.0 g) and 3.0 g sodium sulfide (Na₂S) were added to 60 ml waterand stirred for 20 minutes at room temperature. A film of fluoropolymer(FP1) was submerged in the solution for 5 minutes at 25° C. The treatedfluoropolymer film was then removed and processed in the same manner asdescribed in Comparative Example 1. The treated surface of the film wasanalyzed by ESCA, and the results are reported in Table 1.

EXAMPLE 2

The procedure of Example 1 was repeated, except that the temperature ofthe treatment solution was held at 80° C. for 5 minutes during contactwith the fluoropolymer film. The treated surface of the film wasanalyzed by ESCA and the results are reported in Table 1.

The treated fluoropolymer film was brominated using the procedure ofComparative Example 2. The treated surface of the film was analyzed byESCA, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 3

Comparative Example 3 was an untreated piece of FP1 film (2.0 inches by1.0 inch (5.1 cm by 2.5 cm)).

TABLE 1 ESCA Analysis Example % C % O % N % F % P % S % Br Comparative38 0 0 62 0 0 0 Example 1 Comparative 53.7 7.9 ≦1.2 37.1 ≦0.7 0 0Example 2 (unbrominated) Comparative 50.8 13.0 ≦1.2 33 ≦0.7 0 1.5Example 2 (brominated) Comparative 38 0 0 62 0 0 0 Example 3 Example 146 3.9 ≦1.0 48 0 1.2 0 Example 2 60.9 12.8 ≦1.0 20.5 0 3.8 0(unbrominated) Example 2 60.9 12.8 0 20.5 0 3.8 1.4 (brominated)

EXAMPLES 3–22 and COMPARATIVE EXAMPLES 4–7

Pieces (2.0 inches by 1.0 inch (5.1 cm by 2.5 cm)) of fluoropolymer film(i.e., FP1 or FP2) were treated according to the procedure of Example 1,except that the modifying composition, temperature, and duration oftreatment were varied as reported in Table II.

The treated piece of fluoropolymer film was laminated to a piece (2.0inches by 1.0 inch (5.1 cm by 2.5 cm) of a second polymer film (i.e., P1or P2) using the following general procedure: The fluoropolymer film wassuperimposed on the second polymer film, and a strip ofpolytetrafluoroethylene-coated fiber sheet was inserted about 0.6 cmalong one short edge between the fluoropolymer film to be tested and thesecond polymer film to provide a nonbonded edge to aid in the T-PeelTest. The resultant superimposed film assembly was then laminatedtogether by heating the sheets under 150 psi (1.03 MPa) pressure at 200°C. for 2 minutes between heated platens of a heated hydraulic press. Theresultant hot laminated assembly was then immediately cooled by placingit in intimate contact with a water-cooled metal platen (13–15° C.). Thesample was then gradually warmed to room temperature and the laminatedassembly was tested according to the T-Peel Test.

TABLE 2 Modifying Phase Composition, Transfer Component CatalystTemperature, Duration, T-Peel Test, N/m Example (amount) (amount) ° C.seconds Fluoropolymer P1 P2 Comparative KOH (3 g), Bu₄PBr 25 300 FP1 65035 Example 4 H₂O (60 mL) (1 g) Comparative KOH (3 g), Bu₄PBr 60 60 FP13154 173 Example 5 H₂O (60 mL) (1 g) Comparative KOH (3 g), Pentyl₄NBr25 120 FP1 228 51 Example 6 H₂O (60 mL) (1 g) Comparative KOH (3 g),Pentyl₄NBr 60 30 FP1 NM 244 Example 7 H₂O (60 mL) (1 g) 3 KOH (3 g),Bu₄PBr 25 300 FP1 >3330 71 Na₂S (0.7 g), (1 g) H₂O (60 mL) 4 KOH (3 g),Bu₄PBr 60 60 FP1 >3330 752 Na₂S (0.7 g), (1 g) H₂O (60 mL) 5 KOH (3 g),Bu₄NCl 25 300 FP1 >3330 87 Na₂S (0.7 g), (1 g) H₂O (60 mL) 6 KOH (3 g),Bu₄NCl 60 60 FP1 >3330 524 Na₂S (0.7 g), (1 g) H₂O (60 mL) 7 KOH (3 g),Pentyl₄NCl 25 300 FP1 >3330 2100 Na₂S (0.7 g), (1 g) H₂O (60 mL) 8 KOH(3 g), Pentyl₄NCl 25 30 FP1 >3330 NM Na₂S (0.7 g), (1 g) H₂O (60 mL) 9KOH (3 g), Pentyl₄NCl 25 5 FP1 1067 NM Na₂S (0.7 g), (1 g) H₂O (60 mL)10 KOH (3 g), Pentyl₄NCl 60 5 FP1 >3330 1260 Na₂S (0.7 g), (1 g) H₂O (60mL) 11 KOH (3 g), Pentyl₄NCl 60 30 FP1 >3330 1490 Na₂S (0.7 g), (1 g)H₂O (60 mL) 12 KOH (3 g), Pentyl₄NCl 60 60 FP2 >3330 402 Na₂S (0.7 g),(1 g) H₂O (60 mL) 13 KOH (3 g), Hexyl₄NCl 60 60 FP1 >3330 2100 Na₂S (0.7g), (1 g) H₂O (60 mL) 14 KOH (3 g), Hexyl₄NCl 60 60 FP2 >3330 1280 Na₂S(0.7 g), (1 g) H₂O (60 mL) 15 KOH (3 g), Hexyl₄NBr 60 60 FP1 >3330 2280Na₂S (0.7 g), (1 g) H₂O (60 mL) 16 KOH (3 g), Hexyl₄NBr 60 60 FP2 >33301000 Na₂S (0.7 g), (1 g) H₂O (60 mL) 17 KOH (3 g), Octyl₄NF 60 60FP1 >3330 >3330 Na₂S (0.7 g), (1 g) H₂O (60 mL) 18 KOH (3 g), Octyl₄NF60 60 FP2 2976 1840 Na₂S (0.7 g), (1 g) H₂O (60 mL) 19 KOH (3 g), Me₄NOH25 300 FP1 701 35 Na₂S (0.7 g), (1 g) H₂O (60 mL) 20 KOH (3 g), Me₄NOH60 60 FP1 1260 35 Na₂S (0.7 g), (1 g) H₂O (60 mL) 21 KOH (3 g), Me₄NOH25 300 FP2 228 35 Na₂S (0.7 g), (1 g) H₂O (60 mL) 22 KOH (3 g), Me₄NOH60 60 FP2 173 35 Na₂S (0.7 g), (1 g) H₂O (60 mL)

EXAMPLES 23–28 and COMPARATIVE EXAMPLE 8

Samples of FP1 were exposed to various modifying solutions and phasetransfer catalysts in amounts as reported in Table 3 according to thegeneral procedure of Comparative Example 1, and then analyzed by ESCA.Results are reported in Table 3 (below).

TABLE 3 Modifying Phase EX- Composition, Transfer ESCA Analysis, AM-Component Catalyst 15 degree scattering angle PLE (amount) (amount) % C% O % N % S % F Com- KOH (12 g), none 45 4.3 2.1 0 49 par- H₂0 (60 mL)ative- Ex- am- ple 8 23 Na₂S (4 g), Me₄NOH, 47 5.7 2.4 0.9 44 H₂O (60mL) (1 g) 24 Na₂S (4 g), Bu₄PBr 56 8.2 1.6 4.5 29 H₂O (60 mL) (1 g) 25Na₂S (4 g), Pentyl₄NBr 60 9.2 2.3 6.2 22 H₂O (60 mL) (1 g) 26 Na₂S (4g), Hexyl₄NBr 63 7.8 1.9 6.3 21 H₂O (60 mL) (1 g) 27 Na₂S (4 g),Octyl₄NF 62 6.6 1.7 4.5 25 H₂O (60 mL) (1 g)

EXAMPLES 28–45

Strips (7.6 cm×1.3 cm) of FP1 and FP2 were each modified by treatingthem with a modifying composition consisting of 3.0 g of KOH, 0.7 g ofNa₂S, 1.0 g of Bu₄PBr, and 60 ml water (60° C., 120 seconds). Adhesionof surface-modified FP1 and FP2 films were measured using two strips ofFP1 or two strips of FP2 that were bonded together with adhesivecovering an area of 5.1 cm×1.3 cm placed between the two strips, asreported in Table 4. Bonding of Examples 28–36 (resulting in respectiveExamples 37–45) was achieved by heating the sample at 140° C. in aheated hydraulic press using a pressure of approximately 1 MPa. Thebonded samples were tested according to the T-Peel Test using acrosshead speed of 5.08 cm/minute. Peel strength values of at least fivesamples were averaged and data was expressed in N/m.

TABLE 4 Treated T-Peel Test, N/m Example Film Adhesive FP1 FP2 37Example ADH1 2310 35 28 38 Example ADH2 2540 1730 29 39 Example ADH3 NM193 30 40 Example ADH4 1890 457 31 41 Example ADH5 1400 193 32 42Example ADH6 1020 1070 33 43 Example ADH7 2240 909 34 44 Example ADH81070 209 35 45 Example ADH9  736 173 36

EXAMPLES 46–70 and COMPARATIVE EXAMPLES 9 and 10

Examples 46–70 were conducted generally according to the procedure ofComparative Example 1, with procedural modifications and test results asreported in Table 5 (below).

TABLE 5 Modifying Phase Composition, Transfer Component CatalystTemperature, Duration, Fluoro- T-Peel Test, N/m Example (amount)(amount) ° C. seconds polymer P1 P2 46 KOH (1 g), Bu₄PBr 80 10 FP1 NM2600 Na₂S (4 g), (1 g) H₂O (60 ml) 47 KOH (1 g), Bu₄PBr 80 30 FP1 NM2600 Na₂S (4 g), (1 g) H₂O (60 ml) 48 KOH (4 g), Bu₄PBr 80. 10 FP1 NM2300 Na₂S (1.4 g), (1 g) H₂O (60 ml) 49 KOH (4 g), Bu₄PBr 80 30 FP1 NM2500 Na₂S (1.4 g), (1 g) H₂O (60 ml) 50 KOH (4 g), Bu₄PBr 80. 60 FP1 NM2600 Na₂S (1.4 g), (1 g) H₂O (60 ml) 51 KOH (3 g), Bu₄PBr 80. 10 FP1 NM2500 Na₂S (0.7 g), (1 g) H₂O (60 ml) 52 KOH (3 g), Bu₄PBr 80 5 FP1NM >2500 Na₂S (0.7 g), (1 g) H₂O (60 ml) 53 KOH (2 g), Bu₄PBr 80 30 FP1NM 880 Na₂S (3 g), (1 g) HOCH₂CH₂OH (60 ml) 54 KOH (2 g), Bu₄PBr 80 60FP1 NM 960 Na₂S (3 g), (1 g) HOCH₂CH₂OH (60 ml) 55 KOH (2 g), Bu₄PBr 6060 FP3 >3500 1300 Na₂S (4 g), (1 g) H₂O (60 ml) 56 Na₂S (2.1 g), Bu₄PBr60 30 FP1 >2800 700 H₂O (60 ml) (1 g) 57 KOH (3 g), PTC1 60 120 FP1 NM3200 Na₂S (0.7 g), (1 g) HOCH₂CH₂OH (30 ml) 58 KOH (3 g), PTC1 60 60 FP1NM 3200 Na₂S (0.7 g), (0.2) H₂O (60 ml) 59 KOH (3 g), PTC1 60 60 FP2NM >2500 Na₂S (0.7 g), (0.2) H₂O (60 ml) 60 KOH (3 g), PTC1 60 60 FP1 NM2452 Na₂S (0.7 g), (0.1) H₂O (60 ml) Comparative KOH (3 g), Bu₄PBr 60120 FP3 NM 100 Example 9 H₂O (60 ml) (1 g) 61 KOH (3 g), Bu₄PBr 60 120FP3 NM 440 Na₂S (0.7 g), (1 g) H₂O (60 ml) 62 KOH (3 g), 18-crown-6 60120 FP1 NM 440 Na₂S (0.7 g), ether H₂O (60 ml) (1 g) 63 KOH (3 g),Bu₄PBr 60 120 FP1 960 840 Na₂S₂ (0.8 g), (1 g) H₂O (60 ml) 64 KOH (3 g),Bu₄PBr 60 120 FP1 1300 860 Na₂S₂ (2 g), (1 g) H₂O (60 ml) 65 KOH (3 g),Bu₄PBr 60 120 FP4 400 20 Na₂S (0.7 g), (1 g) H₂O (60 ml) 66 KOH (3 g),Pentyl₄NCl 60 300 FP4 460 40 Na₂S (0.7 g), (1 g) H₂O (60 ml) Comparativenone none NA NA FP5 NM 0.4 Example 10 67 KOH (3 g), Bu4PBr 60 180 FP5 NM3.2 Na₂S (2 g), H₂O (60 ml)

EXAMPLES 68–71

Examples 68–71 were conducted generally according to the procedure ofComparative Example 1, with procedural modifications and test results asreported in Table 6 (below).

TABLE 6 Phase Modifying Transfer T-Peel Strength, Solution CatalystTemperature, Time, Fluoro- N/m Example (amount) (amount) ° C. secondsPolymer P1 P2 68 KOH (3 g), Bu₄PBr 40 120 FP1 880 100 H₂O (60 ml) (1 g)69 KOH (3 g), Bu₄PBr 40 300 FP1 1300 440 H₂O (60 ml) (1 g) 70 KOH (3 g),Bu₄PBr 40 120 FP1 1300 950 Na₂S (0.7 g), (1 g) H₂O (60 ml) 71 KOH (3 g),Bu₄PBr 40 300 FP1 1400 1100 Na₂S (0.7 g), (1 g) H₂O (60 ml)

Various unforeseeable modifications and alterations of this inventionmay be made by those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

1. A method of preparing a composite article comprising: providing afirst substrate having a surface comprising fluoropolymer; contactingthe surface of the first substrate with a modifying compositioncomprising a phase transfer catalyst, a liquid vehicle, and at least oneof a sulfide or polysulfide salt or an anionic conjugate acid of asulfide or polysulfide, wherein the fluoropolymer has a backbonecomprising subunits having the structure —CH₂CFX—, wherein X representsH, Cl, or F; and bonding the first substrate to a second substrate toprovide a composite article, wherein the method is carried out in thesubstantial absence of actinic radiation.
 2. A method according to claim1, wherein the fluoropolymer backbone further comprises at least one ofsubunits having the structure —CF₂CF₂— or subunits having the structure—CF₂CF(CF₃)—.
 3. A method according to claim 1, wherein thefluoropolymer backbone further comprises subunits having the structure—CF₂CF₂— and subunits having the structure —CF₂CF(CF₃)—.
 4. A methodaccording to claim 1, wherein the subunits are monomeric units.
 5. Amethod according to claim 1, wherein the fluoropolymer is prepared frommonomers comprising vinylidene difluoride.
 6. A method according toclaim 5, wherein the monomers further comprise at least one oftetrafluoroethylene or hexafluoropropylene.
 7. A method according toclaim 5, wherein the monomers further comprise tetrafluoroethylene andhexafluoropropylene.
 8. A method according to claim 1, wherein X is H.9. A method according to claim 1, wherein X is F.
 10. A method accordingto claim 9, wherein the fluoropolymer backbone further comprises atleast one of subunits having the structure —CF₂CF₂— or subunits havingthe structure —CF₂CF(CF₃)—.
 11. A method according to claim 9, whereinthe fluoropolymer backbone further comprises subunits having thestructure —CF₂CF₂— and subunits having the structure —CF₂CF(CF₃)—.
 12. Amethod according to claim 11, wherein the subunits are monomeric units.13. A method according to claim 11, wherein the fluoropolymer isprepared from monomers comprising vinylidene difluoride.
 14. A methodaccording to claim 13, wherein the monomers further comprise at leastone of tetrafluoroethylene or hexafluoropropylene.
 15. A methodaccording to claim 13, wherein the monomers further comprisetetrafluoroethylene and hexafluoropropylene.
 16. A method according toclaim 1, wherein bonding comprises adhesive bonding.
 17. A methodaccording to claim 1, wherein bonding comprises heat laminating.
 18. Amethod according to claim 1, wherein the first substrate comprises afilm.
 19. A method according to claim 1, wherein at least one of thefirst or second substrates comprises at least one thermoplastic polymer.20. A method according to claim 19, wherein at least one thermoplasticpolymer comprises polyamide.
 21. A method according to claim 1, whereinthe phase transfer catalyst comprises a tetraalkylphosphonium ortetraalkylammonium salt having at least 16 carbon atoms.
 22. A methodaccording to claim 1, wherein the phase transfer catalyst comprises atetraalkylphosphonium or tetraalkylammonium salt having at least 20carbon atoms.
 23. A method according to claim 1, wherein the phasetransfer catalyst comprises a tetraalkylphosphonium ortetraalkylammonium salt having at least 24 carbon atoms.
 24. A methodaccording to claim 1, wherein the liquid vehicle comprises water.